1) Field of the Invention
The present invention relates to a method of automatically assigning IP, and more particularly, to a method of automatically assigning IP in a ship ad-hoc network, which is capable of preventing an IP collision by transmitting a unique IP in units of block in a tree form in consideration of a ship ad-hoc network environment and of greatly reducing an overhead by preventing messages for sharing an IP allocation state and IP allocation request messages from flooding.
2) Background of Related Art
In general, to use an IP-based service, a ship station must access to a terrestrial station connected to a network to enter the network in a ship ad-hoc network (SANET).
However, since a ship station moving on the sea is difficult to use a static IP address and must enter a sub-net of a terrestrial station through channel allocation, routing and data transmission, the ship station requires an IP address available in the sub-net of the terrestrial station for the purpose of routing and data transmission at IP level.
Differently from a stand-alone mobile ad-hoc network (MANET) which is not connected to Internet of an outside, although IP may be requested to a DHCP server in the ship ad-hoc network, the ship station uses an media access control (MAC) address or determines a temporary IP address by itself to flood the whole network with an address request in order to access to the DHCP server in a multi-hop situation in which routing is not set.
In a limited marine communication environment (the number of time slots and data rate limited), the message flooding for IP assignment may cause a great loss in a network bandwidth.
Therefore, a method of automatically assigning IP, which performs self IP assignment like a mobile ad-hoc network, must be considered rather than a method of assigning IP through a DHCP server.
To this end, as the automatic IP assignment method for a mobile ad-hoc network according to the related art, the studies on an automatic stateful IP assignment method and an automatic stateless IP assignment method have been performed.
However, in the automatic stateful IP assignment method, all nodes periodically broadcast IP states to share the IP states with each other, so that message overhead occurs due to the broadcasting.
In addition, although all nodes can share IP states with each other only when all nodes exist within communication radius of each other, an IP collision is unavoidable in the multi-hop environment in which a hidden terminal problem occurs.
Meanwhile, since the IP collision by a hidden terminal is unavoidable even in the automatic stateless IP assignment method due to random IP assignment, although the IP duplication is examined by using duplicate address detection (DAD) in order to prevent the IP collision, the IP collision still occurs due to network separation and aggregation caused by node movement.
In addition, since the message overhead is greatly increased due to flooding when the duplicate address detection is performed several times, when IP duplicate is examined by using information about a previous legacy protocol message instead of the duplicate address detection in order to reduce the message overhead, there is a need to change previous legacy protocol such as routing.
Thus, the application of the automatic IP assignment method for a mobile ad-hoc network to the ship ad-hoc network without art is inefficient and unsuitable.
Therefore, since, in the automatic IP assignment method, a limited time slot is self-allocated through TDMA-based MAC and data is transmitted at a low speed of 300 kbps or less, when the automatic IP assignment method is designed, there is a need to fully prevent an IP collision in order to reduce the message overheads spent for IP assignment and retransmission due to an IP collision in the routing setting and data transmission.
In addition, since hundreds of ship stations perform communication through VHF bandwidth, there is a need to provide a method capable of sufficiently assigning IP to ship stations accessing to a terrestrial sub-net without insufficiency even when only 16 bits are used for a suffix based on IPv4.
As a related art of the present invention, there is Korean Registered Patent No. KR 1339797 B1.